JPH03132340A - Preparation of recapped tire - Google Patents

Abstract

PURPOSE:To obtain a recapped tire securing good appearance and excellent in durability by using a precured tread having a projection provided to the lower end of the side surface thereof and holding a rubber mold having an outflow preventing member provided to the inner surface thereof between a green tire and an envelope to vulcanize and bond both of them. CONSTITUTION:An annular rubber mold 9 wherein the outer diameter thereof is almost same to that of the lower end projection 8 of the precured tread 5 of a green tire and the inner diameter thereof is smaller than the outer diameter thereof by 10 - 100 mm and an outflow peventing member 10 is provided to the inner surface of the inside end region thereof and the curvature of the inner surface thereof is almost same to that of the green tire is held between the green tire and an envelope 11 is concentric relation to the tire to vulcanize and bond the green tire and the envelope. Even when cushion rubber 4 shows flowability during vulcanization to be extruded to the outside from the gap between the precured tread 5 and a casing 1, the projection 8 provided to the lower end of the side surface of the precured tread 5 comes into contact with the inner surface of the end of the rubber mold 9 on the outer diameter side thereof to develop sealing action and, since the outflow preventing member 10 is provided to the inner surface of the mold 9, the cushion rubber 4 does not exceed the outflow preventing member 10 to protrude toward a rim.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an improvement in a method for manufacturing a retreaded tire, particularly for improving its appearance.

[Prior Art] Conventionally, when manufacturing a retreaded tire, a precure tread having a trapezoidal cross section and no protrusion at the lower end of the side surface was generally used.

In manufacturing, first the remaining tread rubber of the used tire is removed with a buff and the surface is adjusted to create a casing, and then cushion rubber with the same width as the back side of the precure tread is added to the casing. After applying it to the buffed surface, apply the precure tread on top of it, insert an air bag into the inner surface of the casing, attach it to the curing rim, cover the whole thing with an envelope, put it in an autoclave, and separate the casing and envelope. The air pressure inside the air bag is 4 to 15 kg.
A retreaded tire was produced by vulcanizing and bonding a precure tread by heating and pressurizing the tire in an autoclave (7) at a fi pressure of 2 to 14 kg I'/cJ.

[Problems to be Solved by the Invention] However, in this manufacturing method, the air pressure inside the envelope is atmospheric pressure, whereas the outer surface of the precure tread is pressurized at the atmospheric pressure of the autoclave. As a result, the cushion rubber sandwiched between the precure tread and the casing softens due to heating and becomes fluid.
There was a problem in that it was pushed out to both sides and protruded onto the sides of the precure tread and the casing near the precure tread, resulting in an extremely unsightly appearance.

Also, since the casing and the side surface of the precure tread corresponding to the part where this cushion rubber protrudes is not buffed, the adhesion with the cushion rubber is poor, and the cushion rubber may peel off from the side surface of the precure tread or the casing during use of the tire. There was a problem that sand etc. entered during this time and damaged the adhesive interface, causing early tread separation.

An object of the present invention is to provide a method for manufacturing a retreaded tire that prevents the above-mentioned cushion rubber from protruding, ensures a good appearance, and ensures the adhesion of the cushion rubber to prevent tread separation. It is in.

[Means for solving the problem] As a result of intensive studies to achieve the above objective, we used pre-cured tread, which had been vulcanized and molded in advance to have a tread pattern on the surface and a protrusion on the lower edge of the side, to be used on used tires. A method for manufacturing a retreaded tire, in which a green tire is obtained by pasting the tread part on the buffed surface of a casing, which has been adjusted by buffing, via a cushion rubber, and a pre-cured tread is vulcanized and bonded by covering the green tire with an envelope made of an elastic material. , the outer diameter is almost the same as the lower end protrusion of the precure tread of the green tire, and the inner diameter is 10% smaller than the outer diameter.
~100mm smaller, with a leak stopper on the inner surface of the inner end area,
We have invented a manufacturing method in which an annular rubber mold whose inner surface has almost the same curvature as the green tire is sandwiched between the green tire and the envelope concentrically with the tire and vulcanized and bonded.

[Function] Therefore, even if the humidity increases during vulcanization and the cushion rubber becomes soft and fluid and is pushed out from between the precure tread and the casing, the cushion rubber will not be formed on the lower end of the side surface of the precure tread. The protrusions touch the inner surface of the outer diameter end of the rubber mold and their corners dig in to exert a sealing effect, and a leakage stopper is provided on the inner surface of the inner diameter end of the rubber mold. The softened cushion rubber does not protrude beyond the outflow stop to the rim side.

Moreover, since there is a sealed space between the rubber mold and the casing, the cushion rubber pasted on the casing and the cushion rubber extruded from under the pre-cured tread are contained within the sealed space and at the same time are exposed to autoclave pressure. Since it receives equal pressure from the outside, it becomes vulcanized rubber and hardens while strongly adhering to the casing.

Therefore, unlike in the past, the softened cushion rubber does not protrude onto the casing, resulting in an unsightly appearance. Also, since the pressure during vulcanization is sufficiently applied to the edges, there is no possibility of peeling off during use. This ensures that the entire cushion rubber remains securely bonded at all times.

Therefore, a good appearance can be ensured, and the occurrence of tread separation can be prevented.

Furthermore, the upper end of the cushion rubber of the casing terminates along the protrusion of the precure tread rubber, and the lower end terminates along the spill stopper, so it is clearly separated from other parts, and Also, the appearance is good.

Since the cushion rubber does not come into direct contact with the envelope, even if the cushion rubber under the precure tread is heated until it is vulcanized, it will not become over-vulcanized and deteriorate, improving durability.

[Example] Fig. 1 is a schematic cross-sectional view showing a state during vulcanization bonding, Fig. 2 is a partially enlarged view showing the lower end of the precure tread, and Fig. 3 is an enlarged view of the main part thereof.

The explanation will be given below with reference to the drawings. First, the tread portion of a used tire is buffed to make it a rough surface, and a casing 1 is made.

Next, the upper surface of the sidewall 2 of this casing 1 is buffed to make it a rough surface, and then rubber glue is applied to the tread portion 3 and the rough surface portion of the sidewall 2.

After the rubber glue dries, a cushion rubber 4 made of a sheet of unvulcanized rubber composition is applied to that part, and a precure tread 5 is further superimposed on the tread portion 3 to form a green tire 6. As shown in the figure, this precure tread 5 has a trapezoidal cross-sectional outline, and grooves 7 with a tread pattern are carved on the upper surface, and at the lower end of the side surface, as shown in FIGS. 2 and 3, Protrusion 8 with a width of 0.5 to 2 mm and a height of 0.5 to 2 mm
is formed in at least one stage.

Next, an outer diameter ER with a length 2 to 10 mm larger than the distance between both shoulder points SP of the casing 1 and the outer diameter ER.
It has an inner diameter IR that is 10 to 100 nu++ shorter than
An annular rubber mold 9 whose inner surface has almost the same curvature as the outer surface curvature of the casing is made concentric with the casing 1 and temporarily fixed to the casing 1. In addition, this rubber mold 9
is provided with a spill stop 10, for example an annular groove, an annular protrusion, etc., on the inner surface of the inner end region.

Next, a green tire 6 with a thickness of 0.5 mm made of heat-resistant rubber is attached.
A 5-3 mm annular bag envelope 11 is placed over the casing, and then an air bag 12 composed of a tube and a flap is inserted into the casing inner cavity 13.

Next, the inner end of the envelope of the green tire 6 with the air bag 12 and envelope 11 attached is attached to the casing 1.
and the curing rim 15 so as to be sandwiched between the flange 14 and the flange 14.
was inserted into the rim portion 16 of the green tire 6, and the air bag 12 was filled with air at 8 kgf'/cIil to complete preparations for vulcanization.

Next, this tire prepared for vulcanization is placed in an autoclave, and the inside of the envelope 11 is connected to a hose that communicates with atmospheric pressure.
Air of 6 kgf'/cTl is sealed in the autoclave, heated at a temperature of 150° C. for 4 hours to vulcanize the cushion rubber, and thereby fix the precure tread 5 to the casing.

In this way, the precure tread 5 receives pressure from the autoclave from the top surface, while the envelope 1
Since the pressure between the precure tread 5 and the casing 1 is the same as atmospheric pressure, the humidity rises during vulcanization and the cushion rubber softens and becomes fluid, and is pushed out from between the pre-cured tread 5 and the casing 1, but the rubber The protrusion 8 of the precure tread is in contact with the inner surface of the outer end of the mold 9 and its corner bites into a sealing action, and a leak stopper 10 is provided on the inner surface of the inner end of the rubber mold 9. Therefore, the softened cushion rubber 4 does not flow and protrude beyond the stopper to the rim side.

Furthermore, since there is a sealed space between the rubber mold 9 and the casing 1, the cushion rubber 4 pasted on the casing 1 and the cushion rubber 4 extruded from below the pre-cured tread 5 are contained within the sealed space, and at the same time Since it receives pressure equal to the autoclave pressure from the outside,
It hardens into vulcanized rubber while being strongly adhered to the casing.

In addition, this cushion rubber 4 glued on the casing 1
The upper end ends along the protrusion 8 of the precure tread rubber 5, and the lower end ends along the outflow stopper 10, so that it is clearly separated from other parts and has a good appearance. Furthermore, since the pressure during vulcanization is sufficiently applied to the edges, there is no possibility of peeling during use.

Furthermore, in order to further enhance the aesthetic appearance, the inner surface of the rubber mold 9 may be provided with a ring-shaped protrusion, a protrusion such as a diamond pattern, or a recess to give it a patterned finish.

Furthermore, since the cushion rubber 4 does not come into direct contact with the envelope 11, even if the cushion rubber 4 under the pre-cured tread 5 is heated until it is vulcanized, it will not become over-vulcanized and deteriorate, improving durability. It is something that

Note that the above configuration is just an example and is not particularly limited.

Next, in order to investigate the improvement in the adhesion state of the retreaded tire of the present invention according to the above example, tire size 1000R20 was used.
We made a prototype of a retreaded tire and actually mounted it on a regular truck for a driving test.

For comparison, a retreaded tire was manufactured using a conventional method using a precure tread without a protrusion on the lower end, and a running test was conducted under the same conditions as the present invention.

As a result, the tire of the present invention was completely worn out without any damage even after running for 150,000 km. On the other hand, after 10,000 km of running, the tire of the comparative example had peeled off at the part where the cushion rubber had leaked out, and when it was disassembled and inspected after 150,000 km of running, there was a gap between the pre-cured tread and the casing that was approximately 10m
Peeling of m was observed almost over the entire surface.

[Effects of the Invention] As described above, the present invention uses a precure tread having a protrusion at the lower end of the side surface, and furthermore, a rubber mold of an annular body having a stopper on the inner surface of the inner end region is placed between the green tire and the tire envelope. Since the cushion rubber is concentrically sandwiched and vulcanized and bonded, there is no structural protrusion of the cushion rubber that has softened during vulcanization, and a good appearance can therefore be ensured.

Furthermore, since the softened cushion rubber was prevented from extruding, the adhesion state of the entire cushion rubber was improved, tread separation was avoided, and a retreaded tire with excellent durability could be provided.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the state during vulcanization bonding, FIG. 2 is a partially enlarged view showing the lower end of the precure tread, and FIG. 3 is an enlarged view of the main part thereof. 1...Casing 4...Cushion rubber 5
... Precure tread 6 ... Green tire 8 ... Protrusion 9 ... Rubber mold 10 ... Stopper 11 ... Envelope

Claims (1)

[Claims] (1) A pre-cured tread with a tread pattern on the surface and a protrusion on the lower end of the side surface is vulcanized and molded in advance, and a cushion rubber is placed on the buffed surface of the casing, which has been prepared by buffing the tread of a used tire. In the manufacturing method of a retreaded tire, in which a green tire is pasted on the green tire, an envelope made of an elastic material is covered with the green tire, and a precure tread is vulcanized and bonded, the outer diameter is approximately the same as the lower end protrusion of the precure tread of the green tire. An annular rubber mold having the same inner diameter 10 to 100 mm smaller than the outer diameter, a stopper on the inner surface of the inner end region, and an inner surface having almost the same curvature as the green tire is placed between the green tire and the envelope. A method for producing a retreaded tire, which comprises sandwiching the tire concentrically with the tire and vulcanizing and adhering the tire.